Apparatus for relaxing filamentary material



Feb. 3, 1970 1.. a. c mswm. JR 3,492,639

APPARATUS FOR RELAXING FILAMERTARY MATERIAL Original Filed Aug. 17, 1964 2 Sheets-Sheet 1 INVENTOR. j LESTER o. CHIRGWIN,JR.

ATTORNEY Feb. 3, 1970 L. orcmn'swm, JR

APPARATUS FOR RELAXING FILAMENTARYMATERIAL 2 Sheets-Sheet 2 Original Filed Aug. 17, 1964 i Ir I IIIIIIIIIIII nu-n vnuunn-n INVENTOR LESTER 0. CHIRGWIN, JR. I .BY/

ATTORNEY United States Patent 015cc 3,492,689 Patented Feb. 3, 1970 ABSTRACT OF THE DISCLOSURE Apparatus for continuously relaxing endless lengths of filamentary material comprising an elongated chamber having an opening at each end thereof to provide an axial passageway therethrou'gh; means to feed said filamentary material continuously through said elongated chamber along said axial passageway; inlet means-for introducing heated gas at high velocity tosaid chamber near one end thereof, said means including means for heating said gas and means for moving said gas at high velocity; and bafile means within said elongated chamber near said one end thereof to direct the heated gas from said inlet means into an annular fiow moving coaxially without swirling through said elongated chamber. I

This application is a division of'application Ser. No. 389,833, filed Aug. 17, 1964, Patent No. 3,443,009.

This invention relates to an improved process forrelaxing or retracting synthetic filamentary material by a continuous process and to apparatus for performing such process. More particularly, this invention relates to such process and apparatus wherein endless lengths of fila mentary material, such as a tow, are treated with a turbulent fiow of heated gas moving generally parallel to the direction of motion of such filamentary material through a confined zone.

The term tow as used herein is intended to referto a rather large bundle of endless filaments disposed substantially parallel to each other without any interconnecting means preventing easy separation of any given filament or group thereof from the remainder of the bundle. Such a tow may comprise a bundle of as few as several thousand filaments up to several million or more as is well known in the production of synthetic yarns.

In the preparation of fibers of synthetic materials, it is common practice to provide a step wherein such fibers are elongated under tension in order to orient the polymer molecules within such fibers. Illustrative of such fibers are those made from such polymers as thepolyamides, polyesters, cellulose triacetate, acrylonitrile polymers, etc. Frequently, it is necessary or desirable to provide .a heat treatment step for the purpose of relaxing or retracting such fibers in order to ease the strains introduced in the preceding orientation step and to'develop better textile properties in such fibers. Also, such heat treatment serves to reduce the potential shrinkability of such fibers. Prior to the present invention, the desirability of such heat treatment was well known in the synthetic fiber industry and several techniques had been developed to accomplish this result.

Some of these previously known techniques and the deficiencies thereof are detailed in application Ser. No. 389,833, filed Aug. 17, 1964 to which reference should be made for more details.

The present invention overcomes all of the foregoing difficulties in all of the previously known relaxation or retraction processes by providing a process which is very rapid, is useful for retracting or relaxing tow bundles of any number of filaments, which is simple in operation, and which does not require complex equipment while producing a highly uniform relaxation which is controllable at any level of retraction up to the maximum possible with the fibers being treated.

Briefly, the present invention provides a new method and apparatus for continuously relaxing filamentary material which comprises continuously passing an endless length of the filamentary material lengthwise through an elongated confined zone while concomitantly heating the filamentary material solely by exposure to hot gas flowing in turbulent flow longitudinally through the elongated confined zone. Thus, the direction of movement of the filamentary material and the general direction of flow of the hot turbulent gas are generally parallel.

In order to perform this method, the endless length of filamentary material is continuously passed lengthwise through an elongated chamber or confined zone, .which may be of the nature of a pipe open at both ends. Into one end of this chamber is introduced heated gas, such as heated air, at relatively high velocity (moving in turbulent flow) through a specially bafiled entranceway so that the general motion of this turbulent gas is substantially parallel to the axis of the chamber through which the filamentary material is passing.

This chamber preferably is mounted with its axis vertical, with the filamentary material and the hot turbulent gases both moving concurrently in an upward direction for maximum retraction. However, it is possible to perform the method of the present invention by the use ofapparatus wherein the flow of heated gas is countercurrent the tow bundle be exposed to the heated gases for a minimum time which is sufficient to transfer enough heat from the turbulent gas to the filamentary material to produce the desired retraction or relaxation while avoiding the use of a time which is sufficiently long to degrade the fibers at the elevated temperature to which it is being exposed. The temperature of the heated gas which flows in turbulent flow through the confined 'zone for heating up the filamentary material must be at a temperature which is sufficiently high to produce effective retraction or relaxation but it should not be so high as to melt the outside fibers of the tow bundle or degrade the fibers being treated. Thus, numerical limits on the timeand temperature of this operation cannot reasonably be set forth since the time and the temperature depend upon each other and upon the fiber composition. However, within the framework set forth above, suitable time and temperature conditions may readily be determined for any given application since the combined effect of the time and temperature must be sufficient to cause the desiredretraction or relaxation without seriously degrading the fibers. A time of between about 0.1 second and 30 seconds with a temperature between about 250 F. and about 600 F. for the hot turbulent gas as it enters the confining chamber have been found to be satisfactory for the treatment of acrylic fibers which had previously been dried and were moving concurrently with the fiow of the heated turbulent gas. Preferably, about 0.5 to about 5.0 seconds of contact with turbulent gas at a temperature of between about 400 F. and 550 F. can be used for optimum retraction of acrylic fibers.

The movement of the endless length offilamentary material through the confining zone wherein the retraction occurs can be effected by passing the filamentary material around or between rolls located near the inlet end of the confining zone which feed the filamentary material to rolls located near the outlet end of the confining zone. In order to permit retraction, the outlet rolls are rotated at a peripheral speed which is lower than the peripheral speed of the inlet rolls. Control of the relative speeds of these two sets of rolls controls the degree of retraction permitted, which may be any value less than the maximum retraction possible. Thus, if the conditions are such that the maximum retraction possible is 50% of the length of the fiber being treated, the relative speeds of these two sets of rolls may be so adjusted as to produce 40% retraction, 20% retraction, 8% retraction, relaxation at retraction or relaxation at constant length, etc.

The gas moving through the confined zone for heating up the filamentary material being retracted may move at any velocity within a wide range of conditions. The velocity must be sufficient to produce adequate turbulence for effective transfer of heat to all of the fibers within the tow bundle but should not be enough to seriously disarrange the tow bundle or to restretch the filaments by frictional drag when maximum retraction is desired. This velocity range is therefore a function of apparatus design and the size of the tow bundle as well as being a function of the tension generated between the aforementioned two sets of rolls used to control the degree of retraction permitted.'Thus, where maximum retraction is desired and minimum tension results between the inlet rolls and the outlet rolls, lower gas velocities would be used than where higher tensions are applied to limit the amount of retraction during relaxation. When maximum retraction is desired using a confined chamber wherein the continuous filaments and the hot turbulent gas move co-currently in an upward direction, it is preferred that the gas velocity be substantially equal to the sum of the velocity necessary to float the tow and the lengthwise velocity of the endless filaments through the retraction unit. This gas velocity can be readily determined for any particular operation by varying the gas velocity until the tension on the filaments exiting from the confined chamber is reduced to about zero andthe tension on the filament entering the confined chamber is minimized.

For best operation, the fiber should be dry when introduced into the'confining zone for retraction. Otherwise, the heat load for evaporation of variable amounts of moisture contained in the tow would be too variable to permit satisfactorily uniform retraction by the use of this process since the heating medium (heated gas) has a relatively low heat capacity compared with the demands made when water must be evaporated from wet fibers. This highly variable heat load would result in extremely non-uniform retraction. In order to minimize the tendency of the dry fibers to fuse together during this process, the filaments in the tow should contain a suitable lubricant thereon. A listing of suitable lubricants for this high tern perature operation with acrylic fibers may be found in column lines 1 through 28 of U.S. Patent 3,130,249 issued Apr. 21, 1964 to Wishman and Preece.

It has been observed that occasionally acrylic fibers are darkened slightly under certain processing conditions within the framework of the present invention. When this is observed, it frequently can be minimized by the application of antioxidants to the fibers prior to retraction. Illustrative of the antioxidants which have been found useful are: 2,6-ditertiary-butyl-p-cersol, butylated hydroxy tolulene (BHT), butylated hydroxy anisole (BHA), 2,2 thiobis-(4-methyl-6-tertiary-butylphenol), 2,2-methylenebis-(4-methyl 6 tertiary-butylphenol), propyl gallate (with or without citric acid), p-methoxy phenol (hydroquinone monomethyl ether), catechol, isoascorbic acid, and hydroquinone monobenzyl ether.

In order to further prevent fiber degradation and restretching of. thefiberson further processing, it sometimes is desirable to quench the fibers exiting from the confined zone of the retraction unit to minimize the time of exposure to elevated temperature. This quenching may be accomplished by cold or ambient air, water, or other fluid.

The present process is useful for retraction of a tow having any number of filaments up to one million or more. When largetows are being treated, it is preferred that the tow bundle have a cross-section which is relatively ribbon-like rather than one which is relatively ropelike (i.e., preferably a cross-section which is relatively fiat rather than relatively round) in order to facilitate the transfer of heat uniformly to all filaments within the tow bundle from the hot turbulent gases.

For a clearer and-more detailed understanding of the present invention reference may be had to the accompanying drawings wherein:

FIG. 1 is a perspective view of an embodiment of apparatus according to the present invention;

FIG. 2 is a vertical cross-sectional view of the upper portion of the apparatus illustrated in FIG. 1;

FIG. 3 is a vertical cross-sectional view of the l wer portion of the apparatus illustrated in FIG. 1;

FIG. 4 is a cross-sectional view taken on the line IVIV of FIG. 3; and

FIG. 5 is a plan view of a cover plate.

In the embodiment of apparatus for performing the method of the present invention illustrated in the accompanying drawings,]the apparatus comprises generally an elongated tube-like confining chamber 11 through which an endless length 'of filamentary material in the form of an endless tow 13 is passed in an upward direction by means of inlet rolls 15 and outlet rolls 16. concomitantly with the passage of endless tow 13 longitudinally through chamber 11, hot turbulent gas is also passed longitudinally through chamber 11 in an upward direction by means of blower 18 and heater 19 which are connected in a closed loop with chamber 11 by means of conduits 20, 21. If desired, conduit 20 may be provided with a valved opening into which ambient air may be drawn when found necessary or desirable for smoothness of operation of the entire retraction unit.

As illustrated in FIGS. 3 and 4, suitable baffling arrangement is provided in the lower portion of chamber 11 to provide a turbulent flow of hot gas which will move longitudinally through chamber 11. It is important for the performance of this method and the operation of this apparatus that any tendency of the hot turbulent gas to swirl and move helically through chamber 11 be minimized. Accordingly, the bottom end of chamber 11 is provided with a closure plate 24 to which is secured a central tube 25 which is mounted coaxially with chamber 11 around opening 23 in plate 24. Central tube 25 extends upwardlyto a point above the opening where conduit 21 enters chamber 11, and downwardly to opening 23 in closure plate 24 through which tow 13 enters chamber 11. Mounted in the upper portion of the annulus between central tube 25 and the wall of chamber 11 are a plurality of tubular baffle members 26 which extend parallel to the axis of chamber 11 from the upper end of central tube 25 toward the top of the opening where conduit 21 enters chamber 11. Thus, heated gas entering chamber 11 from conduit 21 is distributed around the periphery of chamber 11 and directed upwardly in a direction substantially parallel to the axis of chamber 11 with a minimum of swirling.

A short distance above the upper end of central tube 25, chamber 11 is provided with a bafile plate 28 which is provided with an orifice 29 which is centrally disposed in the path through which tow 13 and heated gas must pass in rising through chamber 11. The relatively small size of orifice 29 causes the heated gas to fiow radially inwardly towards the axis of chamber 11 immediately below bafile plate 28 and then outwardly above baflle plate 28. This non-swirling radial motion of the heated turbulent gas serves to, permit uniform contact between the heated gas and all the filaments in tow bundle 13 so as to permit uniform and rapid heat transfer and retraction of the tow 13.

As illustrated in FIG. 2 a somewhat simpler bafiiing arrangement is provided in the upper portion of chamber 11. This baflle, which serves to separate the spent gas exiting through conduit 20 from tow 13 exiting from chamber 11 towards outlet rolls 16, mainly comprises a closure plate 31 provided with a central opening 32 from which depends a central tube 33, the lowermost end of which extends to below the opening where conduit 20 exits from chamber 11. If found necessary, the upper end of chamber 11 may also be provided with a plurality of tubular baflie members disposed in a manner similar to that of tubular baffie members 26 in the lower end of chamber 11. However, this extra baffling is usually unnecessary for the prevention of swirling motion of the hot turbulent gas passing through chamber 11.

To reduce expiration and inspiration of gases through the openings 23 and 32 at the ends of chamber 11, removable plates 35 may be used. As best seen in FIG. 5, each cover plate 35 is provided with a large centrally disposed slot 36 through which tow bundle 13 can pass with adequate clearance when cover plates 35 are in place. Cover plates 35 are each provided with a pair of fastening slots 37 which are suitably positioned to coact with fastening bolts 38 which are threaded into closure plates 24 and 31. These cover plates 35 are normally removed from the ends of chamber 11 until after tow 13 has been threaded through from inlet rolls 15 to outlet rolls 16, after which cover plates 35 are slid across the ends of chamber 11 with the fastening slots 37 surrounding bolts 38 and the centrally disposed slot 36 surrounding tow 13. When suitably positioned, bolts 38 are tightened securing cover plates 35 in position.

Other obvious modifications exist for the structures specifically illustrated and described herein, and, to the extent they embody the principles of the present invention as defined in the subjoined claims, such modifications are intended to be included within the scope and range of equivalents of the subjoined claims.

What is claimed is:

1. Apparatus for continuously relaxing endless lengths of filamentary material comprising:

(a) an elongated chamber having an opening at each end thereof to provide an axial passageway therethrough;

(b) means to feed said filamentary material continuously through said elongated chamber along said axial passageway, said means comprising a first set of rolls for feeding said filamentary material into said elongated chamber at a first controlled speed and a second set of rolls for feeding said filamentary material out of said elongated chamber at a second controlled speed;

(c) inlet means for introducing heated gas at high velocity to said chamber near one end thereof, said means including means for heating said gas and means for moving said gas at high velocity; and

(d) baflle means within said elongated chamber near said one end thereof to direct the heated gas from said inlet means into an annular flow moving coaxially without swirling through said elongated chamber.

2. Apparatus as defined in claim 1 wherein said first set of rolls is positioned to feed said filamentary material upwardly into the lower portion of said elongated chamber and said second set of rolls is positioned to feed said filamentary material out of the upper portion of said elongated chamber and said inlet means is positioned to introduce said heated gas into the lower portion of said elongated chamber.

3. Apparatus for continuously relaxing endless lengths of filamentary material comprising:

(a) an elongated chamber having an opening at each end thereof to provide an axial passageway therethrough;

(b) means to feed said filamentary material continuously through said elongated chamber along said axial passageway;

(c) inlet means for introducing heated gas at high velocity to said chamber near one end thereof, said means including means for heating said gas and means for moving said gas at high velocity;

(d) bafide means within said elongated chamber near said one end thereof to direct the heated gas from said inlet means into an annular flow moving coaxially without swirling through said elongated chamber; and

(e) a bafiie plate provided with central orifice disposed along said axial passageway, said baflie plate being located near said baffle means to direct said annular flow of heated gas radially inwardly toward the axis of said chamber through said orifice and then radially outwardly within said chamber as said heated gas flows in turbulent flow longitudinally through said chamber.

4. Apparatus as defined in claim 3 wherein said means to feed said filamentary material comprises a first set of rolls for feeding said filamentary material into said elongated chamber at a first controlled speed and a second set of rolls for feeding said filamentary material out of said elongated chamber at a second controlled speed.

5. Apparatus as defined in claim 4 wherein said first set of rolls is positioned to feed said filamentary material upwardly into the lower portion of said elongated chamber and said second set of rolls is positioned to feed said filamentary material out of the upper portion of said elongated chamber and said inlet means is positioned to introduce said heated gas into the lower portion of said elongated chamber.

References Cited UNITED STATES PATENTS 1,814,468 7/1931 Dreyfus et a1. 18-8 XR 3,081,485 3/ 1963 Steigerwald 18-1 XR 3,156,752 11/1964- Cope 18-1XR 3,268,640 8/1966 Gerber. 2,252,684 8/1941 Babcock.

FOREIGN PATENTS 604,488 8/1960 Canada.

OTHER REFERENCES APC-Publication 362,260, Apr. 27, 1943.

WILLIAM J. STEPHENSON, Primary Examiner US. Cl. X.R. 

